Gazprom says the threat is a response to Ukraine's unpaid gas bills, and warns the cut-off could come as early as Monday. The Russian utility says neighboring Ukraine owes it more than $1 billion.

Ukraine is a major transit route for Russian gas headed for western Europe. In 2006, Gazprom briefly cut supplies to Ukraine in a separate dispute, reducing supplies to European Union countries. However, a Gazprom statement Thursday said the pending Ukraine cut-off will not affect its western European customers.

The 2006 Russian cut-off triggered criticism from a range of western governments, which characterized Moscow as an unreliable trading partner.

Ukraine agreed in November to a Russian demand for a 40 percent hike, bumping the price to $179,50 per 1,000 cubic meters of gas - up from $130.